grpc-swift/Sources/gRPC/CountDownLatch.swift

/*
 *
 * Copyright 2016, Google Inc.
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 * modification, are permitted provided that the following conditions are
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 *
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 * notice, this list of conditions and the following disclaimer.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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import Foundation

/// A synchronization primitive used to synchronize gRPC operations
/// Initialize it with a count, a call to wait() will block until
/// signal() has been called the specified number of times.
public class CountDownLatch {
  private var condition : NSCondition
  private var count : Int

  public init(_ count : Int) {
    self.condition = NSCondition()
    self.count = count
  }

  public func signal() {
    self.condition.lock()
    self.count = self.count - 1
    self.condition.signal()
    self.condition.unlock()
  }

  public func wait() {
    var running = true
    while (running) {
      self.condition.lock()
      self.condition.wait()
      if (self.count == 0) {
        running = false
      }
      self.condition.unlock()
    }
  }
}